1. Technical Field
The present invention relates to inner-rotor electric motors and to methods of manufacturing the armature for inner-rotor motors.
2. Description of the Related Art
The armature in an inner-rotor motor is provided with a plurality of teeth that, directed inward, protrude from the inner circumferential surface of a cylindrical core back, and a conductor is wound onto, electrically isolated from, the teeth to form the coils. Known methods of forming the coils include a technique in which winding is carried out by inserting the needle of a winding machine into narrow, groove-like slots between the teeth, and a technique in which a specialized inserter is employed to insert the teeth into conductor wire that has been wound into a special coil form in advance.
In an inner-rotor motor, however, the slots between the teeth open into the confined space along the center shaft, and forming the coil is thus not easy. This makes it difficult to achieve a sufficiently high slot-fill factor. It is also desirable, however, to minimize the gap between the teeth in order to reduce the cogging torque of the motor.
As conventional art for solving the foregoing problem is a technology in which a core member is constituted from a tooth module unitarily formed by circularly joining the inner circumferential edges of a plurality of teeth disposed in a radial fashion, and a core back portion that is separably attached to the outer periphery of the tooth module, and in which a conductor is wound onto each of the teeth, which each have been fitted with an insulating component before the core back portion is attached to the tooth module.
In other conventional art, meanwhile, is a technology in which a stator is manufactured by partially joining with a linker the inner circumferential edges of a radially arranged plurality of teeth and providing insulating components on each tooth, then winding a conductor around and attaching a core back portion onto the linked and insulator-outfitted teeth, and afterwards taking off the linker.
A problem with the foregoing armature is that there are no insulating components with which the armature can be easily manufactured without impairing the electrical isolation between the conductor and the core (the teeth and core back). In addition, for armatures in the conventional technologies, mention has yet to be made regarding the configuration of the insulating components in distributed winding implementations.
When forming coils by winding the conductor onto the teeth in armatures of this sort, the coil may protrude above and below from the top and bottom ends of the teeth. In particular, when the coils are formed by distributed windings, in which the conductor is wound straddling a plurality of teeth, the amount by which the coils protrude is considerable, compared with concentrated windings, in which the conductor is wrapped onto each tooth individually. The protruding coils can be reformed as required, but doing so runs the risk that the reformed coils will come into contact with the top or bottom surfaces of the core back, which is not provided with an insulator.